Electronic publishing has become the standard for developing documents for publication. Publication in this day and age includes not only printed publication but multi-media publications such as CD-ROM or World Wide Web documents as well. Thus, electronic publishing includes content preparation, such as text articles, images and even audio or video in multi-media documents, pre-press layout, proofing and printing.
Color is an important feature in designing documents for publication, whether for print or electronic publication. There are a number of concerns with the integration of color into electronic publishing, not the least of which is the accurate depiction of color on a computer monitor during the design and layout of the document relative to the final printed version. This concern is dependent upon a number of factors, including the spectral qualities relating to how the colors are displayed on a computer monitor screen as compared to the printed colors.
Another concern with color in electronic publishing is the limitations on the definition of colors. Presently, colors must be defined in terms of the components of a single traditional color model. Colors may be converted between these traditional color models, but may not be defined from more than one color model at a time.
A number of traditional color models are currently used in electronic publishing, depending on the document to be created and the printing process to be used. These color models normally fall into two categories, “spot” colors and “process” colors. Spot colors require a separate plate, that is, an image of a page, for each spot color used in the document. Spot colors are typically used for documents that only use one to three colors or for documents using special colors such as fluorescent colors, metallic colors or proprietary colors, such as a company color. Thus, spot colors are normally used for simple documents or for special colors.
Process colors are colors which are created by using percentages of primary color components, such as tints of cyan, magenta, yellow, and black (CMYK) that are blended together to create other colors. Process colors provide many more colors than spot colors for printing purposes and are normally used with documents containing color photography or other items using more than three colors. A document using process colors is separated into separate plates, each containing one of the component colors, such as four separate plates containing differing tints of four primary colors (CMYK). The process of splitting a composite document into its constituent plates and generating an image for each plate is called “separation”.
One of the problems occurring with existing electronic publishing systems occurs when a document is created using process colors, but also requiring a spot color as well. For instance, a special color such as a fluorescent color or a metallic color may be used which can not be created using the process colors. Many documents may also require proprietary colors, such as in a company logo. For instance, a magazine having photography and a company logo may require both color models. Also, many high end publications may use a “varnish” or other special color layer to be applied over an image to create an added effect. A “varnish” may be a translucent color which tints an overall image or document to add a surface effect on the printed image. The addition of spot colors to a document using process colors is not a problem for the actual printing process. An additional plate is created for that particular spot color during the separation.
However, the adding of a spot color onto a document process color is a problem during the electronic design process. Presently, when such a spot color is applied during the design or layout phase of the publishing process, it is difficult to accurately depict on screen. Typically, during the design phase, the process document colors are converted to a color model which can be depicted on a computer monitor screen, such as RGB or LAB. However, the existing algorithms are unable to convert process colors which have been combined with spot colors or with the combination of arbitrary inks. If an on-screen image using process colors is overlayed by the spot color, then that image is blocked from view. Typically, the designer will create two duplicate boxes, one containing the image and the other containing the spot color to be applied. The final image to be printed is not able to be accurately displayed prior to the actual printing of the image. This is of concern since neither the designer nor others later working with the document are sure of the final image.
Since process colors are normally used in most higher end documents, this is an important issue in the publishing industry. Thus, a problem exists in accurately depicting color documents during the electronic design of such documents.
Another problem with the prior electronic publishing systems is the definition of colors digitally. The prior electronic publishing systems utilize standard color models to define colors used in the document and the depiction of the document on a computer screen. These standard color models, such as RGB, LAB, CMYK, Hexachrome, Pantone and others, each use defined color components. For instance, a color defined in the RGB color model uses differing percentages of Red, Green and Blue, the color components of the RGB color model. A color defined in the CMYK color model only uses percentages of Cyan, Magenta, Yellow and/or Black. A color defined in the Hexachrome color model only uses percentages of Cyan, Magenta, Yellow, Black, Orange and Green. Each of the color models use only their respective components in defining a color.
These electronic publishing systems are unable to define a color using “arbitrary” color components. These color components, often referred to as “inks”, are limited for use only within their respective color model. Colors defined in terms of inks in one color model may be converted into the inks of another color model, but a color has not been able to be previously digitally defined in the inks of more than one color model at a time. Thus, a problem exists in the inability to define a color with color components or inks outside of a particular color model.